Even when the threader wire is grabbing the thread, the little down pointer thing that the front thread is hooked around on the left side is too long to release the thread in time for the thread to stay pulled through the needle. I have to be very careful about making sure the thread slides off the hook. For me that is the only function that is really poor. About the big loops on the back, it could be that the top thread in not in the tensions disk securely, or your tension needs to be tightened. This youtube video is for the 4.2, but the expressions all thread the same and it shows the steps and tips for the best threading.
https://www.youtube.com/watch?v=uNHBEUtkUkI